"Plastic" ...........Make sure they don't melt from engine heat. Nylon would be OK "Fiber" would be better
I would have suggested you get a brush kit from say, NAPA, but last time I tried this, they did not fit correctly. I finally had to order 2 or 3 kits, rob parts from 2 to make 1, and then told them to turn "what was left" back in as mis-packaged.
Pisses me off. NAPA USED to be a primo parts outfit
